package Java_Concurrency_in_Practice.monitor;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

/** 基于监视器模式的车辆追踪 */
public class MonitorVehicleTracker {

	private final Map<String, MutablePoint> locations;
	
	public MonitorVehicleTracker(Map<String, MutablePoint> locations) {
		this.locations = deepCopy(locations);
	}
	
	public synchronized Map<String, MutablePoint> getLocations() {
		return deepCopy(locations);
	}
	
	public synchronized MutablePoint getLocation(String id) {
		MutablePoint loc = locations.get(id);
		return loc == null ? null : new MutablePoint(loc);
	}
	
	public synchronized void setLocation(String id, int x, int y) {
		MutablePoint loc = locations.get(id);
		if (loc == null)
			System.out.println("No such ID: " + id);
		loc.x = x;
		loc.y = y;
	}

	private Map<String, MutablePoint> deepCopy(Map<String, MutablePoint> m) {
		Map<String, MutablePoint> result = new HashMap<String, MutablePoint>();
		for (String id : m.keySet()) {
			result.put(id, new MutablePoint(m.get(id)));
		}
		return Collections.unmodifiableMap(result);
	}
}
